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Dna replication
- 1. Genetic Information Transfer 1By- Siddharth Isamaliya
- 2. DNA 2 RNA protein transcription translationreplication reverse transcription Central dogma By- Siddharth Isamaliya
- 3. Replication: synthesis of daughter DNA from parental DNA Transcription: synthesis of RNA using DNA as the template Translation: protein synthesis using mRNA molecules as the template Reverse transcription: synthesis of DNA using RNA as the template 3By- Siddharth Isamaliya
- 6. DNA replication A reaction in which daughter DNAs are synthesized using the parental DNAs as the template. Transferring the genetic information to the descendant generation. 6 replication parental DNA daughter DNA By- Siddharth Isamaliya
- 7. Putting the DNA backbone together ◦ refer to the 3′ and 5′ ends of the DNA OH O PO4 base CH2 O base O P O C O– O CH2 1′ 2′ 4′ 5′ 1′ 2′ 3′ 3′ 4′ 5′ By- Siddharth Isamaliya 7
- 8. Template: double stranded DNA Substrate: dNTP Primer: short RNA fragment with a free 3 ´-OH end Enzyme: DNA-dependent DNA polymerase (DDDP), other enzymes, protein factor 8 DNA replication system By- Siddharth Isamaliya
- 9. Semi-conservative replication Bidirectional replication Semi-continuous replication High fidelity 9By- Siddharth Isamaliya
- 10. Semi-Conservative Replication 10By- Siddharth Isamaliya
- 11. Semiconservative replication Half of the parental DNA molecule is conserved in each new double helix, paired with a newly synthesized complementary strand. This is called semiconservative replication 11By- Siddharth Isamaliya
- 12. Semiconservative replication 12By- Siddharth Isamaliya
- 13. Bidirectional Replication 13 • Replication starts from unwinding the dsDNA at a particular point (called origin), followed by the synthesis on each strand. • The parental dsDNA and two newly formed dsDNA form a Y-shape structure called replication fork. By- Siddharth Isamaliya
- 14. 3' 5' 5' 3' 5' 3' 5' 3' direction of replication Replication fork 14By- Siddharth Isamaliya
- 15. Bidirectional replication 15 • Once the DNA is opened at the origin, two replication forks are formed spontaneously. • These two replication forks move in opposite directions as the syntheses continue. By- Siddharth Isamaliya
- 16. Bidirectional replication 16By- Siddharth Isamaliya
- 17. Replication of prokaryotes 17 The replication process starts from the origin, and proceeds in two opposite directions. It is named θ replication. By- Siddharth Isamaliya
- 18. Replication of eukaryotes 18 • Chromosomes of eukaryotes have multiple origins. • The space between two adjacent origins is called the replicon, a functional unit of replication. By- Siddharth Isamaliya
- 19. Semi-continuous Replication 19 The daughter strands on two template strands are synthesized differently since the replication process obeys the principle that DNA is synthesized from the 5´ end to the 3´end. By- Siddharth Isamaliya
- 20. 5' 3' 3' 5' 5' direction of unwinding 3' On the template having the 3´- end, the daughter strand is synthesized continuously in the 5’-3’ direction. This strand is referred to as the leading strand. Leading strand 20By- Siddharth Isamaliya
- 21. Semi-continuous replication 21By- Siddharth Isamaliya
- 22. • Many DNA fragments are synthesized sequentially on the DNA template strand having the 5´- end. These DNA fragments are called Okazaki fragments. They are 1000 – 2000nt (Nano Tesla) long for prokaryotes and 100-150 nt long for eukaryotes. • The daughter strand consisting of Okazaki fragments is called the lagging strand. Okazaki fragments 22By- Siddharth Isamaliya
- 23. Continuous synthesis of the leading strand and discontinuous synthesis of the lagging strand represent a unique feature of DNA replication. It is referred to as the semi-continuous replication. Semi-continuous replication 23By- Siddharth Isamaliya
- 24. Primase 24 • Also called DnaG • Primase is able to synthesize primers using free NTPs(Nucleoside triphosphate) as the substrate and the ssDNA as the template. • Primers are short RNA fragments of a several decades of nucleotides long. By- Siddharth Isamaliya
- 25. Helicase 25 • Also referred to as DnaB. • It opens the double strand DNA with consuming ATP. • The opening process with the assistance of DnaA and DnaC By- Siddharth Isamaliya
- 27. Replication Fidelity 27 • Replication based on the principle of base pairing is crucial to the high accuracy of the genetic information transfer. • Enzymes use two mechanisms to ensure the replication fidelity. – Proofreading and real-time correction – Base selection By- Siddharth Isamaliya
- 28. Initiation: recognize the starting point, separate dsDNA, primer synthesis, … Elongation: add dNTPs to the existing strand, form phosphoester bonds, correct the mismatch bases, extending the DNA strand, … Termination: stop the replication 28By- Siddharth Isamaliya
- 29. Primase joins and forms a complex called primosome. Primase starts the synthesis of primers on the ssDNA template using NTP as the substrates in the 5´- 3´ direction at the expense of ATP. The short RNA fragments provide free 3´-OH groups for DNA elongation. 29 Primer synthesis By- Siddharth Isamaliya
- 30. The supercoil constraints are generated ahead of the replication forks. Topoisomerase binds to the dsDNA region just before the replication forks to release the supercoil constraint. The negatively supercoiled DNA serves as a better template than the positively supercoiled DNA. 30 Releasing supercoil constraint By- Siddharth Isamaliya
- 31. Primers on Okazaki fragments are digested by RNase. The gaps are filled by DNA-pol I in the 5´→3 ´direction. The nick between the 5´end of one fragment and the 3´end of the next fragment is sealed by ligase. 31 Lagging strand synthesis By- Siddharth Isamaliya
- 32. Cell cycle 32By- Siddharth Isamaliya
- 33. By- Siddharth Isamaliya 33
Editor's Notes
- 互相缠绕、打结、连环